Various examples for Scala discussion

Actors.scala

import scala.actors._ 
import scala.actors.Actor._
case object Poke 
case object Feed

class Kid() extends Actor { 
  def act() {
    loop { 
      react {
        case Poke => { 
          println("Ow...") 
          println("Quit it...") 
        }
        case Feed => {
          println("Gurgle...")
          println("Burp...") 
        }
      } 
    }
  } 
}

val bart = new Kid().start
val lisa = new Kid().start 
println("Ready to poke and feed...") 

bart ! Poke
lisa ! Poke
bart ! Feed
lisa ! Feed

ConcurrencyExample.scala

import scala.io._
import scala.actors._
import Actor._

// START:loader
object PageLoader {
 def getPageSize(url : String) = Source.fromURL(url).mkString.length
}
// END:loader

val urls = List("http://www.amazon.com/", 
               "http://www.twitter.com/",
               "http://www.google.com/",
               "http://www.cnn.com/" )

// START:time
def timeMethod(method: () => Unit) = {
 val start = System.nanoTime
 method()
 val end = System.nanoTime
 println("Method took " + (end - start)/1000000000.0 + " seconds.")
}
// END:time

// START:sequential
def getPageSizeSequentially() = {
 for(url <- urls) {
   println("Size for " + url + ": " + PageLoader.getPageSize(url))
 }
}
// END:sequential

// START:concurrent
def getPageSizeConcurrently() = {
 val caller = self

 for(url <- urls) {
   actor { caller ! (url, PageLoader.getPageSize(url)) }
 }

 for(i <- 1 to urls.size) {
   receive {
     case (url, size) =>
       println("Size for " + url + ": " + size)            
   }
 }
}
// END:concurrent

// START:script
println("Sequential run:")
timeMethod { getPageSizeSequentially }

println("Concurrent run")
timeMethod { getPageSizeConcurrently }
// END:script

Employee.scala

class Person(val name: String) {
  def talk(message: String) = println(name + " says " + message) 
  def id(): String = name
}

class Employee(override val name: String, val number: Int) extends Person(name) {
  override def talk(message: String) {
    println(name + " with number " + number + " says " + message)
  }
  override def id():String = number.toString 
}

NativeXML.scala

val movies =
  <movies>
    <movie genre="sci-fi">Titanic</movie>
    <movie genre="comedy">Alien</movie>
  </movies>

println(movies)
println("----------------------")
println(movies.text)
println("----------------------")
println((movies \ "movie")(0))

PatternMatching.scala

def doChore(chore: String): String = chore match { 
  case "clean dishes" => "scrub, dry"
  case "cook dinner" => "chop, sizzle"
  case _ => "whine, complain"
}

println(doChore("clean dishes")) 
println(doChore("mow lawn"))

QuickSort.scala

def quickSort: List[Int] => List[Int] = {
  case Nil => Nil
  case pivot :: tail =>
    val (smaller, rest) = tail.partition(_ < pivot)
    quickSort(smaller) ::: pivot :: quickSort(rest)
}